PCAST on "Foundational Validity," Evidentiary Reliability, and the Admissibility of "Firearms Analysis"

Finding 6 of President's Council of Scientific Advisors (PCAST), on "firearms analysis," is blunt:

PCAST finds that firearms analysis currently falls short of the criteria for foundational validity, because there is only a single appropriately designed study to measure validity and estimate reliability. The scientific criteria for foundational validity require more than one such study, to demonstrate reproducibility.

(P. 112). In the next breath, the report adds, " Whether firearms analysis should be deemed admissible based on current evidence is a decision that belongs to the courts." Id.

The juxtaposition of these observations is puzzling, for the report also seems to equate "foundational validity" to the legal standard for admissibility in Federal Rule of Evidence 702(c). This part of Rule 702 requires expert testimony to be "the product of reliable principles and methods." Seeking "complete clarity about our intent," PCAST (p. 43) states that

we have adopted specific terms to refer to the scientific standards for two key types of scientific validity, which we mean to correspond, as scientific standards, to the legal standards in Rule 702 (c,d)):
(1) by “foundational validity,” we mean the scientific standard corresponding to the legal standard of evidence being based on “reliable principles and methods,” and
(2) by “validity as applied,” we mean the scientific standard corresponding to the legal standard of an expert having “reliably applied the principles and methods.”

In other words, the PCAST report apparently advances these claims:

1. Evidence E ("firearms analysis") lacks quality Q ("foundational validity," which is a "key type of scientific validity").
2. Q is a sine qua non for the admissibility of all expert evidence under Rule 702.
3. Courts can admit E if they want to.

Can the third claim be reconciled with the first two? I can think of three possibilities:

1. A court might not be bound by Rule 702(c) because the jurisdiction does not follow this rule. (The rule was amended to include the words "reliable principles and methods" to codify the Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993), line of cases (particularly General Electric Co. v. Joiner, 522 U.S. 136 (1997)), but a substantial minority of states apply a different version of the rule.)
2. A court can reject PCAST's claim that "foundational validity" is "the scientific standard corresponding to the legal standard" (at least in the manner that PCAST defines "foundational validity").
3. A court can reject PCAST's claim that the scientific literature does not establish "foundational validity" as the term is defined and applied in the report to "firearms analysis."

By introducing definitions of the terms "validity" and "reliability" that depart from the established meanings in statistics and the social sciences (p. 47 n.107), the PCAST scientists may not have achieved "complete clarity." On the one hand, we are told that established scientific criteria for "validity" correspond to evidentiary "reliability" under Rule 702. On the other, we are assured that the absence of "validity" does not dictate a legal conclusion. For me, this nomenclature falls short of complete clarity.

Index to comments and cases on the PCAST report